This invention relates to compacting fine particles of calcium phosphate. More particularly the invention relates to compacting fine particles of calcium phosphate material, e.g. dicalcium phosphate dihydrate, tricalcium phosphate, monocalcium phosphate, and calcium pyrophosphate to form ribbons or sheets as a preparatory step to utilizing the compacted material for later processing, for example, as excipients in pharmaceutical tablets.
Granules of calcium phosphate sized from about 75 micrometers (um) to about 450 um have great utility as excipients in the manufacture of pharmaceutical tablets, as food supplements for humans or animals, and in the beverage and baking industries. Fine particles, that is particles from about 1 um to about 75 um in size, however, present great problems in handling. Fine particles dust readily, do not flow easily, are burdensome to transport and store, and have too low a bulk density to be utilized directly in tabletting and other processing equipment.
U.S. Pat. No. 2,847,710 granted in 1958 to Pitzer discloses a process for improving the fluid properties of powdered solid materials such as phosphate rock by forming an intimate dry mixture of the powder with about 10 percent of its weight of a solid combustible organic binder-lubricant with a melting point below that of the powdered solid, heating the mixture to melt the organic binder-lubricant, cooling the mixture to a temperature below the melting point of the binder-lubricant, and pelleting the mixture by causing it to flow into small dies, and compressing the pellets.
Gandel discloses in the Chemical Pharmaceutical Journal of the USSR 1969, 3(2), pp 51-56, as abstracted in Chemical Abstracts 70, page 220, 109146 y (1969), a process for granulation of moistened calcium acid phosphate by pressing it through a perforated plate with 0.5 mm holes and then tabletting the compacted material.
U.S. Pat. No. 1,534,828 granted in 1925 discloses the use of phosphoric acid as a binder in briquetting phosphate rock in a "Belgian roll" machine at about 550 atmospheres pressure.
U.S. Pat. No. 3,564,097 granted to Magid in 1971 discloses the use of tricalcium phosphate particles smaller than 75 um as excipients in tablets after they have been mixed with other ingredients and granulated with water. After drying, the large granules are milled, mixed with other ingredients, and the powder compressed into tablets.
U.S. Pat. No. 3,821,414 granted to Monti in 1974 discloses the use of an aqueous solution of locust bean gum as a binder for fine tricalcium phosphate particles 45 um to 75 um in diameter so that the phosphate can be employed as an excipient in making compressed tablets or wafers.
It is an object of the invention to provide a process for utilizing fine particles of calcium phosphate less than 75 um in size. A further object of the invention is to provide compacted sheets or ribbons of calcium phosphate. Still another object of the invention is to make granules of compacted calcium phosphate from about 75 to about 450 um in diameter. An additional object of the invention is to utilize fine particles of dicalcium phosphate dihydrate, tricalcium phosphate, and calcium pyrophosphate as excipients in the production of pharmaceutical tablets or wafers.